Revolving-grate furnace



,March 4, 1958 F. BENOIT-CATTIN REvoLvING-GRATE: FURNACE Filed March 21,1955` f Ma-rch 4, 1958 F. BE NolT-cATTlN REVOLVING-GRATE FURNACEZShQetS-Sheet 2 F/iled March 2l., 1955 r2,825,293?.vVREYOLVHNGGRATEZFURACE. FlixlBenoit-Gattin; Paris,France;lassignor'to'Cmpagnie Generale deconstructiomde Fours-Montrouge(Seine),

France.. l

Application lVIarcli/Zl,y 1955, SeralNo. 495,444

Clairnspriority,V- application France-Marel1`-'25',`v 1954 claims...(Cl. 11o- 35)- This inventionxrelates torevolving-gratejfurnaces,`particularly ofthe'type usedforburning low-gradefuels such-'as domesticrefuse and the like;

One 1 existing type :of such revolving-grate furnace Yhas a tixedfurnacelstructure that `generally comprises four upstanding' walls delininga'rectangular enclosure, and

formed of refractory masonrywork', preferably vwaterjacketed, and arevolving grate in the form of apartcylindrical surface revoluble aboutitshorizont'ally extending axis, and so positioned `as to have anuppermost arcuate portion of the cylindrical surface projecting upbetween said walls to dene the flooror bottom of said enclosure. Therevolving grateincludes a perforate arcuate section extending over kpart of itscircumferential extent to constituteI the actual vgrate; andto either'side of this section there are two solid sections vwhicharediametrically opposed to'each"oth`er, andyvare'interconnectedl by a flatweb across the cylinder. The remainder ofthe cylindrical surface isopen, so as todefne a slagging cavity. The chamber defined between theperforate grate section and the transverse web constitutes' a .blastchamber, and opening ntoit through one of the two end flanges which sealthe opposite ends of 'the cylindrical structure is a conduit throughwhich blast air is delivered into the blast chamber. n

The structure just described is mounted forrotation about its axis sothat it can bey made to'assume 'either of two operative positions,respectively constituting a'ring and a slagging position. In the firingposition; the perforate grate sectionis uppermost; this position`obtains during the actual periods of combustion; during these periodsblast airis being 4discharged into the blast chamber.' This air is thenydischarged through the spaced perforations into the combustion chamberoverlying'the grate and ensures a substantially uniformcombustionthroughout the body of fuel despite the large 4differences j l2,825,293Patented` Mar. 4, 1958 ice allowed to dropintjoa suitable `container orother means of "disposal," andI the perfo'rate 'gratesectionris"returned to its uppermost position. `However it often"occurs.that

the.b'odyjofslag andash'jfi'llingqthe cavity may include various hardobjects, suchl'aspiecesofmetal' or rock or building materiali'or otherrubbish, .and this can' interfere with: the. rotation of: the grate`assembly; Should this condition 'oc`cur,' the" grate assembly' 'isusually, rotateda sligh't'amount in the'reverse' direction so that anyhard object .which may have become jammed against the periphery of jtheslagging cavityisrelased and falls into thek cavity, whereuponlnormalrotation ofthe assembly can generally beresliimedf` However, thenecessity of such reverse rotation constitutesa drawbackl in operationof the furnace and "cloes not always succeed in averting damage .to theassembly/from `objects becoming wedged between the grateand furnacewalls".

Another difculty attending the use of fthe-.known ,type ofrevolving-grate furnacenow beingdiscussedarises out of the factthatjdilferent low-grade fuels may differ in the ash` content therefsThus domestic refuseusuallly has a lowerash content than do shales,Whena lowerash fuel is 'being .burned the time interval betweensuccessive slaggingoperations willlusuallybe longer than ,slagwhich .isallowed .t`o...collect kbetweenslagging operations when a lower-ash-fuelisbeingrused, will be fsolarge and Vcompact. ,as to. prevent4-satisfactoryi draft conditions inpermeability which will generally 'bepresent 'between f different areas of the body of fuel due to thecharacter of the low-grade fuelcontemplated herein. In order further toreduce the effect ofsuch differences in permeability and draft, fuel issuppliedto a considerable depth vover the'grate and.k this necessitatesthe use of high blast pressures. This in turn increases the liability ofyleakage occurring through thev spaces between-the grate structure -andthe furnace walls. Such leaks are particularly obnoxious owing to thehigh content of dust and ashy in the fuel, which dust and ash isdischarged.

from` beingrmaintained... Y

Itis ageneralobject of this. invention toprovide an Limprovedfurnaceparticularly designedrfor burning-low- A grate ifurnace of f the `typedescribed, and particularly a to 'prevent 1or,rninimizethe-.discharge of-ashfand dust, especially in caseswhere low-grade fuelshavinghighash-and dust-contents are being used. Inwthis connection it is.an

limportantv object of the-invention to improve the sanitary conditionsaccompanying the operation vkof.-furnaces `burning V.very low-gradefuelsz- Y Yet a further objectis to improve the operation',` of suchrotary-grate furnaces asregardswthe possi-bility of hard objects`interfering lwith the rotation of. rthe nrotary-grate assembly,therebyfacilitatingthe operation oft -theffurnace and increasing theAservice life of the ,constituentparts thereof.`

Another .object is toprovide means'A whereby :a 'rotary gratelassembly,foraffurnace of-the type described will v be Yadapted forburning fuels differing widely` from- ,one another-in ash content,while-permittingoptimum/operating schedules foreach type of fuel. Inthis connection,

it..is'an"object to providea rotary grate assembly of the l constructandfoperate and. whereinv the parts 1 subjected to severe-wear andteal-are .readily replaceable.

invention as'` well: as =the characteristicfeatures thereof will appearfrom.-thefensuing disclosure' made withreferencef-t'o'fthe accompanyinglzdrawings, wherein one -exem'plary embodiment` ofL the invention isdiagramm'atically becomes lled Vwith a body of slag. As the rotationAVof the grateV assembly is continued this` body of"slag' is' illustratedfor purpose of disclosure but not ofl 'limitation VInthe drawings: v r ny Fg': 11 a longitudinal' sectional' view "of anfirnproved revolvinggrate lfurnace in accordance with this invention, and taken along theline I-I of Fig. 3;

Fig. 2 is a cross sectional view of the improved furnace taken alongthe` line II-II of Fig.` 1;

Fig. 3 is a large-scale view of the detail enclosed in blockA in Fig. 1;i i

`Fig. 4is a similar view of detail B of Fig. 1; and

Fig. 5 is an isometric perspective view of one of the` seal ring membersVused according to the invention, broken away on a diametric plane ofthe ring,`and with the ratio of the cross-section of the ringto thediameter of the latter being considerablyexaggerated for purposes ofclarity.

As shownin the drawings, and particularly in Figs. Zand 3 thereof,a-cylindrical grate according to this invention comprises a recessedcylindrical` body 4 .formed as an integral casting, with a pairof endplates or anges 6. The outer surface 7 of the grate body is preferablymachined or ground to moderately closeitolerances to reduce the amountof clearance space required `between the body of the revolving grate andthe'stationary structure 8 of the furnace.

The actual grate section 9 is formed from one or more removable elementsas shown in Fig. 1, shaped as an extension of the cylindrical surfaces 7and interconnecting these surfaces on one side of a complete cylinder.On the opposite side the cylindrical surface between the surfaces 7 isallowed to remainopen, thereby defining a slag cavity 11. An integraltransverse `web orwall of the body 4 separates this slag cavity 11 froma blast chamber 10 dened in the other side of the cylinder internally ofthe grate; section 9. Moreover, the slag cavity '11 is pro vided with afalse bottom formed by a sheet element 12 secured to the above mentionedtransverse web in spaced4 relation therewith by "means of posts suchas,13.` jDesirably these spacer posts 13 may be readily removed andreplaced with spacer posts of ditferentsizes so as to adjust thecapacity of the slag cavity in accordance with the ashycontent in the`particular type of fuel used.V

The grate body `is fitted with removable cntter blade members asillustrated at 14, which are adapted to co- Aoperate with backingmembers 15 inserted as `shown between the water-jacketing 16 (which maybe replaced by an ordinary refractorylining if preferred), andthe'stationarily supporting structure 8. The cutter members are made ofhard steel or other suitable alloy possessing highlhardness at elevatedtemperaturesyand highresistance to wear and corrosion.

Means are provided according to the invention for minimizing theleakageapt to occur from the ends of the revolving-grate cylinder andfor ensuring` that any` leakage there occurring will be limited to pureair rather than heavily dust and ash-laden smoke as wouldfotherwise bethe case.

For this purpose, the stationary structure 8 is` formed at each end withanannular groove 17 (see Figf4) in which is received a seal ring 18havinga rectangular cross sectional shape, such that the ring is freely``rnov able inta directiongparallel to the axis of rotation of thecylindrical grate.` As` shown in Fig. '1 such a ring is provided at eachAend-of the grate cylinder.` Each `ring is applied against 'the adjacentend face ofthey 'grate cylinder body by a set of presser members orpistons'19` subjected to thetaction-of lsprings .20K "Thenumber ofpresser members andfsprings in `each set depends on the diameter of thegrateso lthat the spacing between consecutive. presser pistons will in`each case be small enough to prevent.objectionable` distortion of theseal rings.

Each ring'lS, i is laterally provided... with an arcuate cnedreinforcing sections.

A blast conduit 22 tapped from the main blastdelivery line 22a, at apointizahead of the control Avalve 24,

connects with the end wall of the groove 17 as shown in Fig. 3. The airblast delivered `by pipe 22 flows through a plurality of holes such as25 formed through the ring 18 to issue therefrom into the groove 21. Thering 18 is moreover formed with la further set of` small orifices orducts 26 extending radially of the ring through the outer wall of thegroove 21. The air issuing out through these ducts4 acts to prevent theoutow of leakage gases which otherwise would tend to leak out throughthe gap 27 between the grate cylinder body and the stationary furnacestructure; leakage of combustion gas is thus pre vented at thecost ofonly an insignifcantly small loss of blast air.

It willbe'understood that many `modifications can be made in the detailsof `the specific embodiment of the invention illustrated and describedin detail herein without exceeding the scope of the invention. It willbe appreciated that while the `various improved features described maybe'applied separately within the scope of the invention,` the combinationof said features in a revolving grate furnaceachieves a greatly improvedunit in which the combustion capacity andefliciency, as well as thelabor conditions attendant on the operation thereof, are greatlyimproved over comparable furnaces of the prior art. t

What I claim is:

1. In a `furnace of the type described, the combination of stationarystructure including means defining two spaced side furnacewalls and twospaced end furnace walls, a revolving 'grate assembly comprising a bodyincluding two spaced symmetrical elements having outer zontal axis, aflat web interconnecting said elements and defining a plane parallelwith the geometrical axis of the cylindrical` surface, perforate gratemeans connected with both of said elements and defining an arcuatesurface portion of said cylindrical surface between said oppositesurface portions-toont:` side of said web, the space delined betweensaid grate means, said elements and said one side of the web providing ablast chamber, blast conduit means connected with said chamber fordischarging blast air thereinto, the space defined between said elementsand the other side of the web being left open to provide a slag cavityoppostely relatedto said grate ineens, means mounting said assembly forrotation with respect to said furnace walls about said axis between afiring position wherein said grate means lies uppermost between saidwalls and a slagging position wherein said slag cavity lies uppermostbetween said walls, a pair of end anges for said grate assembly inadjacent relation to said respective end walls and defining `therewith apair of leakage spaces` out of said blast chamber, each of said endwalls having an annular circumferential groove therein facing theperipheral portion of a related one of said end flanges, a ring memberreceived in each groove for limited axial sliding movement towards andaway from said related peripheral end ange portion, means wherein saidresilient means urging the ring members includes a plurality of pistonlike members slidably mounted in each said end wall for engagement withthe axially louter surface-of` the related rlng member in angularlyequispaced relation around said ring member and springs associated withsaid piston members for urging the latter .Y against said ring members.

3.1111 a furnace the combination as claimed in claim l,

ywherein each ring member has an arcuate recess in the axial end facethereof directed towards said related end flange, and said orices aredefined by longitudinal ducts formed through said ring member andopening into said recess, and transverse ducts formed through a radiallyouter side of said recess and opening into said leakage space.

4. In a furnace the combination as claimed in claim 1,

wherein said rotational mounting means comprise end journal means forsaid assembly, at least one of said journal means having a recesscommunicating with said blast chamber, and wherein said blast conduitmeans is connected with said recess in the journal means.

5. In a furnace, the combination as claimed in claim 1, wherein saidassembly further comprises a at member defining a false bottom for saidslag cavity, and interchangeable means supporting said flat member inparallel spaced relation to said web within said slag cavity.

6. In a furnace, the combination as claimed in claiml, furthercomprising cutter blade means removably secured to said elements of theassembly at the respective sides of said slag cavity and having cuttingedges lying along said cylindrical surface, and backing means supportedby said furnace side walls in a position for cooperating with saidcutter means on rotation of said assembly to and from said slaggingposition.

7. In a furnace of the type described, the combination of fixedstructure defining furnace walls, a revolving assembly defining a partcylindrical surface including a first arcuate section defining aperforate grate and two diametn'cally opposite solid arcuate sectionsconnected with opposite arcuate ends of said first section, a attransverse web interconnecting said solid sections and defining a blastchamber with said first arcuate section, blast conduit means connectedwith said chamber, means for mounting said assembly for rotation about ahorizontal axis coaxial with said cylindrical surface between a firingposition wherein said first grate section is uppermost between saidfurnace walls and a position wherein said rst section is lowermost, endflanges for said assembly in sealed relation with said first arcuatesection and said solid arcuate sections, said end flanges beingpositoned adjacent to, and defining leakage spaces with, respective endones of said furnace walls, a ring member received between each end walland the adjacent end flange for limited axial movement therebetween,said ring members having apertures therein, and means for dischargingblast air through said end walls and said aper' tures in the ringmembers into said leakage spaces.

8. ln a furnace of the type described, the combination of fixedstructure defining furnace walls, a revolving grate assembly defining apart cylindrical surface including a perforate arcuate section providinga grate and two diametrically opposed solid arcuate sections connectedwith respective ends of said perforate section, a Hat transverse webinterconnecting said solid sections and defining a blast chamber withsaid perforate section, blast conduit means connected with saidperforate section, blast conduit means connected with said blastchamber, means for mounting said assembly for rotation about ahorizontal axis coaxial with said cylindrical surface between a firingposition wherein said perforate section is uppermost between said wallsand a slagging position wherein said perforate section is lowermost, endflanges for said assembly in sealed relation with said perforate sectionand said solid sections, said end flanges being positioned adjacent to,and defining leakage spaces with, respective end ones of said furnacewalls, each end furnace wall having a circumferential groove thereinfacing the related end ange and communicating with the related leakagespace, a ring member positioned in each groove for limited axialmovement therein towards and away from said end flange, meansresiliently urging said rings against said end flanges, said ringmembers having apertures extending therethrough, and means fordelivering blast air into said grooves for discharge through saidapertures into said leakage spaces. v

9. In a furnace, the combination as claimed in claim 8, wherein saidmeans urging the rings includes a plurality of spring-pressedpiston-like members slidably mounted in each end wall for engagementwith a surface of said ring in angularly equispaced relationtherearound, and arranged for urging said ring members towards said endflanges.

10. In 4a furnace, the combination as claimed in claim 8, wherein eachring member has an arcuate recess in the axial end face thereof directedtowards the related end flange, and each ring member has longitudinalducts extending through said ring member and opening into said recess,and transverse ducts extending through a radially outer side of saidrecess and opening into said related leakage space to define saidapertures.

References Cited in the le of this patent UNITED STATES PATENTS 250,389Perkins Dec. 6, 1881 1,207,358 Atterbury Dec. 5, 1916 FOREIGN PATENTS560,035 Great Britain Mar. 1 6, 1944

